A history of low back pain affects pelvis and trunk coordination during a sustained manual materials handling task

PURPOSE: The purpose of this study was to compare the coordination between the trunk and the pelvis during a sustained asymmetric repetitive lifting task between a group with a history of low back pain (LBP; HBP) and a group with no history of LBP (NBP). METHODS: Volunteers lifted a 11-kg box from ankle height in front to a shelf 45° off-center at waist height, and lowered it to the start position at 12 cycles/min for 10 min. Lifting side was alternated during the trial. Continuous relative phase was used to calculate coordination between the pelvis and trunk rotation at the beginning (Min 1), middle (Min 5), and end of the bout (Min 9). RESULTS: While there were no main effects for group, a significant interaction between time and group indicated that, in the frontal plane, the NBP group coordination was more anti-phase toward the end of the bout, with no such differences for the HBP group. Analysis of sagittal-axial (bend and twist) coordination revealed the HBP group coordination was more in-phase at the end of the bout over the entire cycle and for the lifting phase alone, with no such differences for the NBP group. CONCLUSION: Differences between groups demonstrate residual consequences of LBP in an occupational scenario, even though the HBP group was pain-free for >6 months prior to data collection. More in-phase coordination in the HBP group may represent a coordination pattern analogous to “guarded gait” which has been observed in other studies, and may lend insight as to why these individuals are at increased risk for re-injury.